/*-
 * Copyright (c) 1999, 2000, 2001, 2002, 2004, 2005
 * 	Lev Walkin <vlm@lionet.info>. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Id: strtotime.c,v 1.6 2006/12/11 07:11:52 vlm Exp $
 */

#ifndef	__EXTENSIONS__
#define	__EXTENSIONS__
#endif

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <sys/types.h>

#ifdef	HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef	HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef	HAVE_TIME_H
#include <time.h>
#endif

#ifdef	HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef	HAVE_ERRNO_H
#include <errno.h>
#else
#ifndef	EINVAL
#define	EINVAL	1
#endif
#endif

#include <assert.h>

#include <sf_time.h>

#ifndef	HAVE_TM_ZONE
#ifndef	HAVE_TZNAME
#warning "Assume, there is char *tzname[2]"
#define	HAVE_TZNAME
#warning "Please, please report this situation to vlm@lionet.info!"
#warning "This iz due to my lazyness in checking the unusual states..."
#endif
#endif


#ifndef	HAVE_LOCALTIME_R
/*
 * Emulate localtime_r() using localtime().
 */
static struct tm *
_sf_localtime_r(const time_t *clock, struct tm *result) {
	struct tm *tmp;
	tmp = localtime(clock);
	if(tmp)	/* Assume result is not NULL */
		memcpy(result, tmp, sizeof(struct tm));
	return result;
}
#define	localtime_r	_sf_localtime_r
#endif


/*
 * Default date (for parsing something like "23:59").
 */
#define	NO_VALUE	0x7fffffff
static struct {
	int year;
	int mon;
	int mday;
	int cur_off;
} _sf_def = { NO_VALUE, 0, 0, 0 };


static int _sf_chartype_table[256] = {
	0, 0, 0, 0, 0, 0, 0, 0,	/* 07 */
	0, 1, 1, 1, 0, 1, 0, 0,	/* 15 */
	0, 0, 0, 0, 0, 0, 0, 0,	/* 23 */
	0, 0, 0, 0, 0, 0, 0, 0,	/* 31 */
	1, 0, 0, 0, 0, 0, 0, 0,	/* 39 */
	0, 0, 0, 0, 0, 0, 0, 0,	/* 47 */
	2, 2, 2, 2, 2, 2, 2, 2,	/* 55 */
	2, 2, 0, 0, 0, 0, 0, 0,	/* 63 */
};
#define	_sf_isspace(foo)	(_sf_chartype_table[(foo)] & 1)
#define	_sf_isdigit(foo)	(_sf_chartype_table[(foo)] & 2)


static inline int
_sf_recognize_month(unsigned char *dts) {

	switch(*dts & ~32) {
	case 'A':
		switch(dts[1]) {
		case 'p': if(dts[2] == 'r') return 3; return -1;
		case 'u': if(dts[2] == 'g') return 7;
		default: return -1;
		}
	case 'D': if(dts[1] == 'e' && dts[2] == 'c') return 11; return -1;
	case 'F': if(dts[1] == 'e' && dts[2] == 'b') return 1; return -1;
	case 'J':
		switch(dts[1]) {
		case 'a': if(dts[2] == 'n') return 0; return -1;
		case 'u':
			switch(dts[2]) {
			case 'l': return 6;
			case 'n': return 5;
			}
		default: return -1;
		}
	case 'M':
		if(dts[1] != 'a') return -1;
		switch(dts[2]) {
		case 'r': return 2;
		case 'y': return 4;
		default: return -1;
		}
	case 'N': if(dts[1] == 'o' && dts[2] == 'v') return 10; return -1;
	case 'O': if(dts[1] == 'c' && dts[2] == 't') return 9; return -1;
	case 'S': if(dts[1] == 'e' && dts[2] == 'p') return 8; return -1;
	default: return -1;
	}
}


/* Water-proof atoi() */
static inline int
_sf_natoui(unsigned char *str, int num) {
	int n = 0, na;

	while(num-- > 0) {
		na = *str++;
		if(!_sf_isdigit(na))
			return -1;
		n = (n * 10) + (na - '0');
	}

	return n;
}

static inline time_t
_sf_recognize_tz(unsigned char *dts) {

	if(*dts == '+' || *dts == '-') {
		time_t tmp;

		tmp = _sf_natoui(dts+1, 4);
		if(tmp < 0) return -1;

		tmp = (tmp / 100) * 3600 + (tmp % 100) * 60;
		if(*dts == '-') tmp = -tmp;

		dts += 5;
		while(*dts == ' ') dts++;
		return tmp;
	} else if(*dts == '(' || (*dts >= 'A' && *dts <= 'Z')) {

		if(*dts == '(') dts++;

		if(!*dts || !dts[1] || !dts[2]
		|| (dts[3] >= 'A' && dts[3] <= 'Z'))
			return 0;

		/* RFC 822 zones */
		switch(*dts) {
		case 'G': if(dts[1] == 'M' && dts[2] == 'T') return 0;
			return -1;
		case 'E':
			switch(dts[1]) {
			case 'S': if(dts[2] == 'T') return - 5 * 3600;
			case 'D': if(dts[2] == 'T') return - 4 * 3600;
			default: return -1;
			}
		case 'C':
			switch(dts[1]) {
			case 'S': if(dts[2] == 'T') return - 3 * 3600;
			case 'D': if(dts[2] == 'T') return - 5 * 3600;
			default: return -1;
			}
		case 'M':
			switch(dts[1]) {
			case 'S': if(dts[2] == 'T') return - 7 * 3600;
			case 'D': if(dts[2] == 'T') return - 6 * 3600;
			default: return -1;
			}
		case 'P':
			switch(dts[1]) {
			case 'S': if(dts[2] == 'T') return - 8 * 3600;
			case 'D': if(dts[2] == 'T') return - 7 * 3600;
			default: return -1;
			}
		default: return -1;
		}
	}

	return -1;
}


static inline long
_sf_recognize_time(unsigned char *dts) {
	long l = 0;
	int tmp;

	if(!*dts)
		return -1;

	if((tmp = _sf_natoui(dts, 2)) < 0 || tmp > 24)
		return -1;

	l |= tmp << 16;
	if(dts[2] != ':' && dts[2] != '-') return -1;
	dts+=3;

	if((tmp = _sf_natoui(dts, 2)) < 0 || tmp > 60)
		return -1;

	l |= tmp << 8;
	if(dts[2] != ':' && dts[2] != '-') {
		l |= 5 << 24;
		return -1;
	}
	dts+=3;

	if((tmp = _sf_natoui(dts, 2)) < 0 || tmp > 60)
		return -1;

	l |= tmp;
	l |= 8 << 24;

	return l;
}

/*
 * Ensures year is within correct range.
 */
static inline int
_sf_year_range_gen(int year) {
	if(year > 1000) {
		year -= 1900;
	} else {
		/* Dirty hack to convert 80 to 1980. */
		if(year < 38) {
			year += 100;
			return year;
		}
	}

	if(year < 2 || year > 138)
		return 0;

	return year;
}

static inline int
_sf_year_range_big(int year) {
	year -= 1900;

	if(year < 2 || year > 138)
		return 0;

	return year;
}

static inline int
_sf_year_range_small(int year) {

	/* Dirty hack to convert 80 to 1980. */
	if(year < 38) {
		year += 100;
		if(year < 2)
			return 0;
		else
			return year;
	}

	if(year < 2 || year > 138)
		return 0;

	return year;
}

static inline int
_sf_is_year_leap(int year) {
    return (year % 400)
	? ((year % 100)
		? ((year % 4)?0:1)
		: 0 )
	: 1;
}

/* Fast version of mktime() */
static time_t
_sf_mktime(struct tm *tm) {
	static int mdshift[] = { 0, 31, 59, 90, 120,
		151, 181, 212, 243, 273, 304, 334 };
	time_t t;

	t  = (tm->tm_year - 70) * 365
		+ ((tm->tm_year - 69) >> 2)
		+ mdshift[tm->tm_mon];

	/* Leap day for this year. */
	if ( tm->tm_mon >= 2
		&& _sf_is_year_leap( tm->tm_year + 1900 ) )
		++t;

	t = ((((((t + (tm->tm_mday - 1)) * 24)
		+ tm->tm_hour) * 60)
		+ tm->tm_min) * 60)
		+ tm->tm_sec;

	return t - _sf_def.cur_off;
}

/*
 * Zone info cache
 */
static int _sf_param_stt_zcache;
void strtotime_zoneinfo_cache(int on_off) { _sf_param_stt_zcache = on_off; }

/*
 * Convert given time into time_t.
 * dts (date/time string) can be in numerous representations,
 * some of them are mentioned in strtotime(3) manual page.
 */

time_t
strtotime(char *dtsp) {
	static time_t lcupd;	/* Last year/zone cache update */
	static time_t hour_end_in;
	unsigned char *dts;
	struct tm tm;
	time_t tmp;
	time_t sugOffset = 0;		/* Suggested offset from GMT */
	enum {
		TFORM_ERROR,		/* Seems like error */
		TFORM_RFC822,		/* Seems like RFC 822 */
		TFORM_ISO8601,		/* Seems like ISO 8601 */
		TFORM_CTIME,		/* Seems like unix ctime() format */
		TFORM_SYSLOGD,		/* Seems like syslogd format */
	} timespec_form;

	/*
	 * Cache current year, time offset.
	 */
	if(_sf_def.year == NO_VALUE) {
		time(&tmp);
		if(localtime_r(&tmp, &tm) == NULL)
			goto fail;
		_sf_def.year = tm.tm_year;
		_sf_def.mon = tm.tm_mon;
		_sf_def.mday = tm.tm_mday;
		_sf_def.cur_off =
#ifdef	HAVE_TM_ZONE
			tm.tm_gmtoff;
#else	/* HAVE_TM_ZONE */
			- timezone;
#endif	/* HAVE_TM_ZONE */
		hour_end_in = 3600 - (60 * tm.tm_min + tm.tm_sec);
		lcupd = tmp;
	} else if(_sf_param_stt_zcache == 0) {
		time(&tmp);
		if((tmp - lcupd) > hour_end_in) {
			_sf_def.year = NO_VALUE;
			return strtotime(dtsp);
		}
	}

	if(!dtsp) goto fail;

	/* That's a good start. */
	for(; *dtsp == ' '; dtsp++);
	dts = dtsp;

	/*
	** Forms:
	** form = 0: something like error
	** form = 1: ? RFC 822
	** form = 2: ? ISO 8601
	** form = 3: ? ctime()
	** form = 4: ? syslogd format (Mar 23 18:15:00)
	*/

	if(*dts >= 'A') {
		timespec_form = TFORM_RFC822;
	} else if(_sf_isdigit(*dts)) {
		int n;
		for(n = 0; _sf_isdigit(dts[n]); n++);
		if(n != 8	/* YYYYMMDD */
			&& (!dts[n]
				||
			   (_sf_isspace(dts[n]) && !dts[n+1]))) {
			if((unsigned long)atol(dts) < 0x7fffffff)
				return (time_t)atol(dts);
		}
		timespec_form = TFORM_ISO8601;
	} else {
		/*
		 * Unknown date/time representation,
		 * started neither from digital,
		 * nor from alphabetic character.
		 */
		goto fail;
	}


	/*
	 * Initialize temporary tm structure with default date.
	 */
	memset(&tm, 0, sizeof(struct tm));
	tm.tm_isdst = -1;
	tm.tm_year  = _sf_def.year;
	tm.tm_mon   = _sf_def.mon;
	tm.tm_mday  = _sf_def.mday;

 switch(timespec_form) {
 case TFORM_RFC822:

	for(;; dts++) {
		switch(*dts) {
		case '\0': goto fail;
		default: continue;
		case ' ':
			/* Maybe, it is just ctime()? */
			dts = dtsp; goto tform_ctime;
		case ',':
			dts++;
		}
		break;
	}

	for(; *dts == ' '; dts++);

	if(*dts) {
		if(dts[1] == ' ') {
			tmp = _sf_natoui(dts++, 1);
		} else {
			tmp = _sf_natoui(dts, 2);
			dts+=2;
		}
	} else {
		goto fail;
	}

	if(tmp < 1)
		goto fail;
	else
		tm.tm_mday = tmp;

	for(; *dts == ' ' || *dts == '-'; dts++);
	if(!*dts) goto fail;

	tmp = _sf_recognize_month(dts);
	if(tmp < 0)
		goto fail;
	else
		tm.tm_mon = tmp;

	while(*dts >= 'A' || *dts == ' ' || *dts == '-') dts++;
	if(!*dts) goto fail;

year:

	if((tmp = _sf_natoui(dts, 4)) == -1) {
		if((tmp = _sf_natoui(dts, 2)) < 0)
			goto fail;
		if((tm.tm_year = _sf_year_range_small(tmp)) == 0)
			goto fail;
		dts+=2;
	} else {
		if((tm.tm_year = _sf_year_range_big(tmp)) == 0)
			goto fail;
		dts+=4;
	}

	while(*dts == ' ') dts++;

	if((tmp = _sf_recognize_time(dts)) == -1)
		goto fail;

	dts += ((unsigned int)tmp) >> 24;
	tm.tm_hour = (tmp >> 16) & 0xff;
	tm.tm_min = (tmp >> 8) & 0xff;
	tm.tm_sec = tmp & 0xff;
	
	while(*dts == ' ') dts++;

	sugOffset = _sf_recognize_tz(dts);

	break;

 case TFORM_ISO8601:

	/* Year */
	if((tmp = _sf_natoui(dts, 4)) == -1) {
		/* hh:mm... form */
		if(strlen(dts) >= 5) {
			if(dts[2] == ':') {
				/* HH:MM */
				goto tme;
			} else if(dts[2] == '/' || dts[2] == '.') {
				/* DD.MM */
				goto dte;
			} else if(dts[2] == '-' || dts[2] == ' ') {
				if(_sf_isdigit(dts[3]))
					goto dte;
				tm.tm_mday = _sf_natoui(dts, 2);
				tm.tm_mon = _sf_recognize_month(dts + 3);
				if((tm.tm_mday & tm.tm_mon) == -1) goto fail;
				dts += 6;
				if(*dts != '-' && *dts != ' ') goto fail;
				dts++;
				goto year;
			}
		}
		goto fail;
	} else {
		if((tm.tm_year = _sf_year_range_big(tmp)) == 0)
			goto fail;
	}

	dts+=4;
	if(!*dts) goto fail;

	if(*dts == '-' || *dts == '/') dts++;
	else {
		if(*dts == '+' || *dts == 'Z') goto zone;
		if(*dts == 'T') {
			dts++;
			goto tme;
		}
	}

dte:

	/* Month */
	if((tmp = _sf_natoui(dts, 2)) == -1) {
		if(dts[-1] == '-') goto fail;
		if(!_sf_isspace(*dts)) goto fail;
		break;
	} else {
		if((--tmp) < 0)
			goto fail;
		else
			tm.tm_mon = tmp;
	}

	dts+=2;
	if(!*dts) break;

	if(*dts == '-' || *dts == '/' || *dts == '.') {
		dts++;
	} else {
		if(*dts == '+' || *dts == 'Z') goto zone;
		if(*dts == 'T') {
			dts++;
			goto tme;
		}
	}

	/* Month Day */
	if((tmp = _sf_natoui(dts, 2)) == -1) {
		if(dts[-1] == '-') goto fail;
		if(!_sf_isspace(*dts)) goto fail;
		break;
	} else if(tmp) {
		tm.tm_mday = tmp;
	} else {
		goto fail;
	}

	dts+=2;
	if(dts[-3] == '.' || (dts[-3] == '/' && dts[0] == '/')) {
		int __tmp = tm.tm_mday;
		tm.tm_mday = tm.tm_mon + 1;
		tm.tm_mon = __tmp - 1;

	}

	if(*dts == '.' || *dts == '/') {
		if((tmp = _sf_natoui(dts + 1, 4)) == -1) {
			if((tmp = _sf_natoui(dts + 1, 2)) == -1)
				goto fail;
			if(_sf_isdigit(dts[3]))
				goto fail;
			if((tm.tm_year = _sf_year_range_small(tmp)) == 0)
				goto fail;
			dts += 3;
		} else {
			if((tm.tm_year = _sf_year_range_big(tmp)) == 0)
				goto fail;
			dts += 5;
		}
	}

lp:
	if(!*dts) {
		sugOffset = -1;
		break;
	}
	if(*dts == 'T') {
		dts++;
		goto tme;
	}
	if(_sf_isdigit(*dts)) goto tme;
	if(*dts == '+') goto zone;
	if(*dts == 'Z') break;
	if(*dts++ == ' ')
		goto lp;
	break;

tme:

	if((tmp = _sf_natoui(dts, 2)) == -1)
		goto fail;
	else
		tm.tm_hour = tmp;

	dts+=2;

	if(!*dts) break;
	if(*dts == ':') {
		dts++;
	} else {
		if(*dts == '+' || *dts == '-') goto zone;
		if(*dts == 'Z') break;
	}

	if((tmp = _sf_natoui(dts, 2)) == -1) {
		if(dts[-1] == ':') goto fail;
		if(!_sf_isspace(*dts)) goto fail;
		break;
	} else {
		tm.tm_min = tmp;
	}

	dts+=2;

	if(!*dts) goto zone;
	if(*dts == ':') dts++;
	else {
		if(*dts == '+' || *dts == '-') goto zone;
		if(*dts == 'Z') break;
	}

	if((tmp = _sf_natoui(dts, 2)) == -1) {
		if(dts[-1] == ':') goto fail;
		if(!_sf_isspace(*dts)) goto fail;
		break;
	} else {
		tm.tm_sec = tmp;
	}

	dts+=2;

	if(!*dts) {
		/*
		 * Time in this form without the GMT offset
		 * is the LOCAL time
		 */
		sugOffset = -1;
		break;
	}
	while(*dts == ' ') dts++;

zone:

	if(!*dts) {
		/*
		 * Time in this form without the GMT offset
		 * is the LOCAL time
		 */
		sugOffset = -1;
		break;
	}

	if(*dts == 'Z') {
		sugOffset = 0;
		break;
	}
	if(*dts != '+' && *dts != '-') {
		if(_sf_isspace(*dts)) break;
		goto fail;
	}

	sugOffset = _sf_recognize_tz(dts);

	break;

 case TFORM_CTIME:
 tform_ctime:

	tmp = _sf_recognize_month(dts);
	if(tmp != -1) {
		tm.tm_mon = tmp;
		goto tform_syslogd;
	}

	for(;; dts++) {
		switch(*dts) {
		case '\0': goto fail;
		default: continue;
		case ' ': dts++;
		}
		break;
	}

	if((tmp = _sf_recognize_month(dts)) < 0)
		goto fail;
	else
		tm.tm_mon = tmp;

	while(*dts >= 'A' || *dts == ' ') dts++;

	if(*dts && dts[1] == ' ') {
		tmp = _sf_natoui(dts++, 1);
	} else {
		tmp = _sf_natoui(dts, 2);
		dts+=2;
	}

	if(tmp < 1)
		goto fail;
	else
		tm.tm_mday = tmp;

	while(*dts && *dts == ' ') dts++;

	if((tmp = _sf_recognize_time(dts)) == -1)
		goto fail;

	dts += ((unsigned int)tmp) >> 24;

	tm.tm_hour = (tmp >> 16) & 0xff;
	tm.tm_min = (tmp >> 8) & 0xff;
	tm.tm_sec = tmp & 0xff;

	while(*dts == ' ') dts++;
	if(!*dts) goto fail;

 ctime_year:

	if((tmp = _sf_natoui(dts, 4)) < 0) {
		if((tmp = _sf_natoui(dts, 2)) < 0)
			goto fail;
		if((tm.tm_year = _sf_year_range_small(tmp)) == 0)
			goto fail;
		dts+=2;
	} else {
		if((tm.tm_year = _sf_year_range_big(tmp)) == 0)
			goto fail;
		dts+=4;
	}

	while(*dts && *dts == ' ')
		dts++;

	sugOffset = _sf_recognize_tz(dts);

	break;

 /* syslogd format (Mar 23 18:15:00) */
 case TFORM_SYSLOGD:
 tform_syslogd:

	while(_sf_isspace(*dts) == 0)	/* Skip month */
		dts++;
	while(_sf_isspace(*dts))	/* Skip space before the date */
		dts++;

	if(!*dts)
		goto fail;

	if(
		((tmp = _sf_natoui(dts, 2)) == -1)
		&& ((tmp = _sf_natoui(dts, 1)) == -1)
	)
		goto fail;
	else
		tm.tm_mday = tmp;

	while(*dts && *dts != ' ')	/* Skip date */
		dts++;

	while(*dts && *dts == ' ')	/* Skip space before the time */
		dts++;

	if(!*dts)
		goto fail;

	if((tmp = _sf_recognize_time(dts)) == -1)
		goto fail;

	dts += ((unsigned int)tmp) >> 24;

	tm.tm_hour = (tmp >> 16) & 0xff;
	tm.tm_min = (tmp >> 8) & 0xff;
	tm.tm_sec = tmp & 0xff;

	if(*dts == ' ' && _sf_isdigit(dts[1])) {
		dts++;
		goto ctime_year;
	}

	sugOffset = -1;
	break;

 case TFORM_ERROR:
	assert(!"should not happen");
	goto fail;
 } /* switch() */

	if(sugOffset == -1) {
		/*
		 * Time in this form without the GMT offset
		 * is the LOCAL time.
		 */
		sugOffset = 0;
	} else {
		sugOffset -= _sf_def.cur_off;
	}

	return _sf_mktime(&tm) - sugOffset;

fail:

	errno = EINVAL;

	return 0;
}